1.Field of the Invention
The present invention is generally related to induction heating systems, and, more specifically, to an induction heating system that can be used for, among other things, brazing applications.
2. Discussion of the Background
Brazing is a process for joining metal parts. A brazing process uses heat and a filler metal to join metals parts together. Typically, the filler metal has a melting temperature above 840xc2x0 F. (450xc2x0 C.), but below the melting point of the parts being joined. The filler metal is either pre-placed into the joint between the parts or fed into the joint as the parts are being heated. The application of the heat causes the filler to melt and flow into the joint, usually by capillary action, thereby joining the parts.
Brazing is probably the most versatile method of metal joining today, for a number of reasons. First, brazed joints are strong. Second, brazed joints are ductile; that is, they are able to withstand considerable shock and vibration. Additionally, brazing is ideally suited to the joining of dissimilar metals.
Conventionally, the parts to be joined and the filler metal are heated in a normal atmosphere using a conventional heat source, such as a flame. Flame brazing in a normal atmosphere causes the undesirable side effects of oxidation, scaling, and carbon build-up on the parts. To clean the parts of this carbon build-up, applications of joint-weakening flux and expensive acid cleaning baths have been required.
One solution to the above problem is to use a batch vacuum furnace. However, batch vacuum furnaces have significant limitations because of their large size, batch manufacturing methods, poor efficiency, and lack of quality control.
What is desired, therefore, is a system and/or method that overcomes these and other disadvantages of conventional brazing systems.
The present invention provides an induction heating system that can be used to braze metals and that overcomes many of the disadvantages of conventional brazing systems described above. Furthermore, the induction heating system improves quality and lowers production cost for many brazing requirements. The system is designed to quickly, accurately and cost effectively heat individual parts, and to replace flame brazing procedures and batch vacuum furnaces.
Because the system can braze parts in an inert atmosphere or in no atmosphere (e.g., in a vacuum), no flux or acid cleaning bath is necessary and oxidation on the part is eliminated. Further, by including a gas quenching feature, the system prevents the annealing of parts and produces high quality brazed parts that meet desired hardness specifications.
In one embodiment, the induction heating system includes a vacuum chamber; a support surface located within the chamber for providing a surface onto which a part to be heated is placed; moving means connected to the support surface for moving the support surface within the chamber; a vacuum system connected to the chamber for exhausting gases from the chamber; an electrically conductive coil located inside of the chamber or located adjacent to the chamber; an induction heating unit, coupled to the coil, for providing an alternating current to the coil; a temperature sensing means for sensing the temperature of the part; an operator interface for displaying a user interface comprising one or more selectable push button icons and for receiving input from an operator; and a controller interfaced to the operator interface, the vacuum system, the induction heating unit, the moving means, and the temperature sensing means.
Advantageously, the controller is programmed to perform a procedure in response to an operator selecting one of the selectable push button icons. The procedure includes the steps of: sending a signal to the moving means to cause the moving means to move the support surface so that the part is appropriately located with respect to the coil; sending a signal to the vacuum system to cause the vacuum system to exhaust gases from the chamber; monitoring the pressure within the chamber; after the pressure within the chamber reaches a predetermined threshold, sending a signal to the induction heating unit to cause the induction heating unit to provide to the coil an alternating current having sufficient power to heat the part to a predetermined temperature; waiting for a predetermined amount of time; and after the predetermined amount of time has elapsed, sending a signal to the induction heating unit causing the induction heating unit to stop providing the alternating current to the coil.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.